EP3568301A1 - Éléments d'impression lithographique de type à ablation ayant une sensibilité à l'exposition améliorée et procédés associés - Google Patents

Éléments d'impression lithographique de type à ablation ayant une sensibilité à l'exposition améliorée et procédés associés

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Publication number
EP3568301A1
EP3568301A1 EP18705194.1A EP18705194A EP3568301A1 EP 3568301 A1 EP3568301 A1 EP 3568301A1 EP 18705194 A EP18705194 A EP 18705194A EP 3568301 A1 EP3568301 A1 EP 3568301A1
Authority
EP
European Patent Office
Prior art keywords
imaging
layer
printing member
imaging layer
absorber
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP18705194.1A
Other languages
German (de)
English (en)
Inventor
Travis Softic
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Presstek LLC
Original Assignee
Presstek LLC
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from US15/403,263 external-priority patent/US10124571B2/en
Application filed by Presstek LLC filed Critical Presstek LLC
Publication of EP3568301A1 publication Critical patent/EP3568301A1/fr
Pending legal-status Critical Current

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41C—PROCESSES FOR THE MANUFACTURE OR REPRODUCTION OF PRINTING SURFACES
    • B41C1/00—Forme preparation
    • B41C1/10—Forme preparation for lithographic printing; Master sheets for transferring a lithographic image to the forme
    • B41C1/1008—Forme preparation for lithographic printing; Master sheets for transferring a lithographic image to the forme by removal or destruction of lithographic material on the lithographic support, e.g. by laser or spark ablation; by the use of materials rendered soluble or insoluble by heat exposure, e.g. by heat produced from a light to heat transforming system; by on-the-press exposure or on-the-press development, e.g. by the fountain of photolithographic materials
    • B41C1/1033—Forme preparation for lithographic printing; Master sheets for transferring a lithographic image to the forme by removal or destruction of lithographic material on the lithographic support, e.g. by laser or spark ablation; by the use of materials rendered soluble or insoluble by heat exposure, e.g. by heat produced from a light to heat transforming system; by on-the-press exposure or on-the-press development, e.g. by the fountain of photolithographic materials by laser or spark ablation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41N—PRINTING PLATES OR FOILS; MATERIALS FOR SURFACES USED IN PRINTING MACHINES FOR PRINTING, INKING, DAMPING, OR THE LIKE; PREPARING SUCH SURFACES FOR USE AND CONSERVING THEM
    • B41N1/00—Printing plates or foils; Materials therefor
    • B41N1/003—Printing plates or foils; Materials therefor with ink abhesive means or abhesive forming means, such as abhesive siloxane or fluoro compounds, e.g. for dry lithographic printing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41C—PROCESSES FOR THE MANUFACTURE OR REPRODUCTION OF PRINTING SURFACES
    • B41C2210/00—Preparation or type or constituents of the imaging layers, in relation to lithographic printing forme preparation
    • B41C2210/02—Positive working, i.e. the exposed (imaged) areas are removed
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41C—PROCESSES FOR THE MANUFACTURE OR REPRODUCTION OF PRINTING SURFACES
    • B41C2210/00—Preparation or type or constituents of the imaging layers, in relation to lithographic printing forme preparation
    • B41C2210/14—Multiple imaging layers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41C—PROCESSES FOR THE MANUFACTURE OR REPRODUCTION OF PRINTING SURFACES
    • B41C2210/00—Preparation or type or constituents of the imaging layers, in relation to lithographic printing forme preparation
    • B41C2210/16—Waterless working, i.e. ink repelling exposed (imaged) or non-exposed (non-imaged) areas, not requiring fountain solution or water, e.g. dry lithography or driography
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41C—PROCESSES FOR THE MANUFACTURE OR REPRODUCTION OF PRINTING SURFACES
    • B41C2210/00—Preparation or type or constituents of the imaging layers, in relation to lithographic printing forme preparation
    • B41C2210/20—Preparation or type or constituents of the imaging layers, in relation to lithographic printing forme preparation characterised by inorganic additives, e.g. pigments, salts
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41C—PROCESSES FOR THE MANUFACTURE OR REPRODUCTION OF PRINTING SURFACES
    • B41C2210/00—Preparation or type or constituents of the imaging layers, in relation to lithographic printing forme preparation
    • B41C2210/22—Preparation or type or constituents of the imaging layers, in relation to lithographic printing forme preparation characterised by organic non-macromolecular additives, e.g. dyes, UV-absorbers, plasticisers

Definitions

  • a printable image is present on a printing member as a pattern of ink-accepting (oleophilic) and ink-rejecting (oleophobic) surface areas. Once applied to these areas, ink can be efficiently transferred to a recording medium in the imagewise pattern with substantial fidelity.
  • Dry printing systems utilize printing members whose ink-repellent portions are sufficiently phobic to ink as to permit its direct application.
  • the non-image areas are hydrophilic, and the necessary ink-repellency is provided by an initial application of a dampening fluid to the plate prior to inking.
  • the dampening fluid prevents ink from adhering to the non-image areas, but does not affect the oleophilic character of the image areas.
  • Ink applied uniformly to the printing member is transferred to the recording medium only in the imagewise pattern.
  • the printing member first makes contact with a compliant intermediate surface called a blanket cylinder which, in turn, applies the image to the paper or other recording medium.
  • the recording medium is pinned to an impression cylinder, which brings it into contact with the blanket cylinder.
  • Plate-imaging devices amenable to computer control include various forms of lasers.
  • Dry plates which utilize an oleophobic topmost layer of fluoropolymer or, more commonly, silicone (polydiorganosiloxane), exhibit excellent debris-trapping properties because the topmost layer is tough and rubbery; ablation debris generated thereunder remains confined as the silicone or fluoropolymer does not itself ablate. Where imaged, the underlying layer is destroyed or de-anchored from the topmost layer.
  • a common three-layer plate for example, is made ready for press use by image-wise exposure to imaging (e.g., infrared or "IR”) radiation that causes ablation of all or part of the central layer, leaving the topmost layer de-anchored in the exposed areas.
  • imaging e.g., infrared or "IR”
  • the de-anchored overlying layer and the central layer are removed (at least partially) by a post-imaging cleaning process — e.g., rubbing of the plate with or without a cleaning liquid— to reveal the third layer (typically an oleophilic polymer, such as polyester).
  • a post-imaging cleaning process e.g., rubbing of the plate with or without a cleaning liquid— to reveal the third layer (typically an oleophilic polymer, such as polyester).
  • Nitrocellulose can formulated to form crosslinked or uncrosslinked polymeric structures and can be applied using traditional coating techniques.
  • a radiation absorber e.g., in the case in infrared (IR) or near-IR imaging radiation, carbon black pigment or an IR-absorptive dye.
  • IR infrared
  • near-IR imaging radiation carbon black pigment or an IR-absorptive dye.
  • the latter is often preferred for the high loading levels that can be achieved with concomitant reduction in minimum laser power.
  • the combination with nitrocellulose can lead to fabrication and stability challenges. Without being bound by any particular theory, it is believed that nitrocellulose retains its fluffy cotton-like conformation even when dissolved, and further, that this conformation is essential for performance during plate imaging.
  • the nitrocellulose structure can collapse, impairing performance (the affected region does not absorb and respond to incident energy) and creating a telltale red spot, which leads to an unwanted void on the printed press sheet.
  • the collapse is exacerbated by temperatures above 270 °F (making drying difficult) and can be substantially worsened by the presence of elemental metals such as copper, silver, or tin.
  • nitrocellulose-containing lithographic printing members can be enhanced, and red-spot areas reduced or eliminated, through the use of dual adjacent imaging layers, both including an absorber and at least one containing a binder (which may include or consist essentially of a melamine resin).
  • One of the imaging layers contains an IR-absorptive dye and no nitrocellulose, while the other layer contains nitrocellulose and an IR-absorptive pigment.
  • Printing members in accordance herewith can therefore retain the benefits of using both an IR- absorbing dye (which can be loaded at high levels to reduce the minimum imaging fluence without impairing layer durability or coatability) and nitrocellulose (with its beneficial ablation characteristics) in substantial weight proportions— i.e., proportions that would be untenable in a single layer.
  • an IR- absorbing dye which can be loaded at high levels to reduce the minimum imaging fluence without impairing layer durability or coatability
  • nitrocellulose with its beneficial ablation characteristics
  • the invention relates to a method of imaging a printing member.
  • the method comprise the steps of providing a printing member comprising (i) a subtrate having an oleophilic surface, (ii) first and second imaging layers disposed over the substrate, the first imaging layer comprising a binder and a near-IR absorber including a dye, the second imaging layer comprising nitrocellulose and a near-IR absorber that does not include a dye, and (iii) disposed over the imaging layers, an oleophobic third layer; (b) exposing the printing member to imaging radiation in an imagewise pattern, the imaging radiation at least partially ablating the imaging layers where exposed; and (c) cleaning the printing member to remove the third layer and at least a portion of the imaging layers where the printing member received imaging radiation, thereby creating an imagewise pattern on the printing member.
  • the invention pertains to a lithographic printing member.
  • the printing member comprises a substrate having an oleophilic surface; first and second imaging layers disposed over the substrate, wherein (i) the first imaging layer comprises a binder and a near-lR absorber including a dye, (ii) the second imaging layer comprises nitrocellulose and a near-IR absorber that does not include a dye, and (iii) the first and second imaging layers are at least partially ablatable by exposure to near-IR radiation at a fluence level no greater than 160 mJ/cm 2 ; and (c) disposed over the imaging layers, an oleophobic third layer.
  • the first imaging layer has a first side in contact with the third layer and a second side, opposed to the first side, in contact with the second imaging layer
  • the second imaging layer has a first side in contact with the first imaging layer and a second side, opposed to the first side, in contact with the substrate.
  • the substrate may be a metal (e.g., aluminum) sheet having a grained surface in contact with one of the imaging layers.
  • the binder of the first imaging layer may be a melamine resin.
  • the second imaging layer further comprises a binder, e.g., a melamine resin.
  • the nitrocellulose may have a nitration level above 10.7% but less than 12.3% by weight.
  • the the near-IR absorber of the first imaging layer further comprises carbon black.
  • the near-IR absorber of the first imaging layer may consist or consist essentially of a dye.
  • the near-IR absorber of the second imaging layer may consist or consist essentially of carbon black.
  • the cleaning fluid may be an aqueous liquid, e.g., plain tap water.
  • the aqueous liquid comprises water and a component that eases the removal of silicone.
  • the aqueous liquid may include not more than 20% (or not more than 15%) by weight of an organic solvent, e.g., an alcohol, and the alcohol may be a glycol (e.g., propylene glycol), benzyl alcohol and/or phenoxyethanol.
  • the aqueous liquid may comprise a surfactant. It can be cold or, preferably, heated (usually up to 42 oC/108 oF, even 46 oC/115 oF) or less than these temperatures.
  • a typical chemical cleaning fluid is (by weight) diethylene glycol 60%, 2-(2-aminoethoxy)ethanol 10%, deionized water 29.75%, and SURFYNOL 104E surfactant 0.25% (although better results are typically obtained using tap water alone).
  • the chemical cleaning fluid may also be heated.
  • the term "plate” or ' ⁇ member” refers to any type of printing member or surface capable of recording an image defined by regions exhibiting differential affinities for ink and/or fountain solution. Suitable configurations include the traditional planar or curved lithographic plates that are mounted on the plate cylinder of a printing press, but can also include seamless cylinders (e.g., the roll surface of a plate cylinder), an endless belt, or other arrangement.
  • Ablation of a layer means either rapid phase transformation (e.g., vaporization) or catastrophic thermal overload, resulting in uniform layer decomposition.
  • decomposition products are primarily gaseous.
  • Optimal ablation involves substantially complete thermal decomposition (or pyrolysis) with limited melting or formation of solid decomposition products.
  • a resin phase consisting essentially of a melamine resin and a resole resin may include other ingredients, such as a catalyst, that may perform important functions but do not constitute part of the polymer structure of the resin.
  • an imaging layer consisting essentially of a melamine (or other) resin and an IR absorber may contain other ingredients that do not contribute to ablation in response to imaging radiation; and an imaging layer consisting essentially of nitrocellulose and an IR-absorbing pigment may contain other ingredients that do not contribute to ablation in response to imaging radiation (i.e., it could not contain an IR- absorbing dye).
  • a single crosslinked polymer network consisting essentially of, for example, melamine means that the melamine composition is the only crosslinked polymer network in the composition. Percentages refer to weight percentages unless otherwise indicated. Description of Drawing
  • FIG. 1 illustrates a negative-working printing member 100 according to the present invention that includes a substrate 102, imaging layers 104 and 106, and a topmost layer 108.
  • Layers 104, 106 are sensitive to imaging (generally IR) radiation as discussed below, and imaging of the printing member 100 (by exposure to IR radiation) results in imagewise full or partial ablation of the layers 104, 106.
  • the resulting de-anchorage of topmost layer 108 facilitates its removal by rubbing or simply as a result of contact during the print "make ready" process.
  • the ablation debris of layer 104 and/or layer 106 may be chemically compatible with water in the sense of being acted upon, and removed by, an aqueous liquid following imaging.
  • Substrate 102 (or a layer thereover) exhibits a lithographic affinity opposite that of topmost layer 108. Consequently, ablation of layers 104, 106 followed by imagewise removal of the layer 108 to reveal an underlying layer or the substrate 102, results in a lithographic image. Even if layers 104, 106 are ablated only partially, they (and their ablation debris) are also ink-accepting, so their continued presence following imaging and cleaning does not adversely affect printing.
  • Substrate 102 provides dimensionally stable mechanical support to the printing member.
  • the substrate should be strong, stable, and flexible.
  • the topmost surface is generally oleophilic (and may also be hydrophilic).
  • Suitable materials include, but are not limited to, polymers, metals and paper.
  • the term "substrate” refers genetically to the ink-accepting layer beneath the radiation-sensitive layers 104, 106, although the substrate may, in fact, include multiple layers (e.g., an oleophilic film laminated to an optional metal support, such as an aluminum sheet having a thickness of at least 0.001 inch, or an oleophilic coating over an optional paper support).
  • the preferred substrate is a grained metal (e.g., aluminum) sheet, which is both oleophilic and hydrophilic (though the latter affinity is not relevant here).
  • a metal substrate 102 beneath a nitrocellulose imaging layer would require an intervening heat-insulating layer to prevent excessive heat dissipation and the consequent increase in minimum laser fluence.
  • metal substrates are preferably grained.
  • the grained surface may be created by at least one of anodizing, electrograining or roughening with a fine abrasive.
  • the grained surface may be created by electrograining followed by anodizing.
  • a structured or grained surface can also be produced by controlled oxidation, a process commonly called "anodizing.”
  • An anodized aluminum substrate consists of an unmodified base layer and a porous, “anodic" aluminum oxide coating thereover; this coating readily accepts water.
  • Anodized plates are, therefore, typically exposed to a silicate solution or other suitable (e.g., phosphate) reagent that stabilizes the hydrophilic character of the plate surface.
  • silicate treatment the surface may assume the properties of a molecular sieve with a high affinity for molecules of a definite size and shape— including, most importantly, water molecules.
  • Anodizing and silicate treatment processes are described in U.S. Patent Nos. 3,181,461 and 3,902,976.
  • Poly(vinyl phosphonic acid) post-anodic treatment is desirable.
  • Preferred substrate materials include aluminum that has been mechanically, chemically, and/or electrically grained with subsequent anodization.
  • an ungrained metal sheet with a primer layer thereover to reduce heat transmission and consequent dissipation, or a polymeric (e.g., polyester) substrate 102, e.g., coated with a primer layer to enhance adhesion.
  • a polymeric (e.g., polyester) substrate 102 e.g., coated with a primer layer to enhance adhesion.
  • Layer 104 contains nitrocellulose and is responsive to imaging radiation, typically near-IR radiation.
  • layer 104 has a cured resin phase consisting essentially of a melamine resin and, if desired, a resole resin, the latter being present in an amount ranging from 0% to 28% by weight of dry film.
  • a binder resin is included, the nitrocellulose is present in proportions similar to those of the resin phase.
  • the nitrocellulose has a moderate viscosity in solution, and furthermore, since it has hydroxyl groups in the molecule, it is especially likely to form a crosslinked structure. Nitrocellulose of any molecular weight suitable to the application, given the considerations described herein, may be employed.
  • the nitrocellulose is not an explosive grade (less than 12.5% nitration), but instead in the range suitable for industrial use (more than 10.7% but less than 12.3% nitration).
  • Suitable melamine resins include methylated, low-methylol, high-imino melamine materials.
  • CYMEL crosslinkers from Cytek Industries, Inc., especially CYMEL 385, CYMEL 303, CYMEL 328, CYMEL 327, CYMEL 325 and CYMEL 323, may be employed.
  • Melamine crosslinking may be facilitated by a sulfonic acid catalyst, typically a p-toluenesulfonic acid catalyst.
  • layer 104 is a crosslinked layer.
  • layer 104 preferably comprises 20 to 60%, and especially 25 to 50%, nitrocellulose and 25 to 55%, especially 35 to 50%, CYMEL.
  • Layer 106 is a cured polymeric layer that includes an IR-absorbing dye, typically at high loading levels, and generally does not contain nitrocellulose or IR-absorbing pigment. Layers 104, 106 are in direct contact. Layer 106 can be any polymer capable of stably retaining, at the applied thickness, the IR-absorptive dye adequate to cause ablation of the layer in response to an imaging pulse.
  • the melamine resins described in connection with layer 104 are suitable.
  • layer 106 may comprise 25 to 55%, and especially 35 to 50%, CYMEL and 30 to 60%, especially 35 to 55%, IR-absorbing dye. Carbon black may also be present, for example, in the range of 1 to 10%, especially 1 to 5%.
  • Typical drying temperatures for layers 104 and 106 are in the range from 270 to 290 °F (132 to 144 °C) with residence times from 35 to 45 seconds.
  • Typical dry coat weights for layers 104 and 106 are 1.1 ⁇ 0.2 g/m 2 .
  • layers 104, 106 both exhibit water compatibility following ablation. Furthermore, in embodiments where either or both layers are only partially ablated, they are either (a) sufficiently water-compatible to be fully removed during cleaning, or (b) oleophilic if some of layer(s) remain even after cleaning. It is found that carbon black enhances, or even confers, the desired water compatibility of layer 104 or the ablation debris thereof. Layers 104, 106 should exhibit good adhesion to adjacent layers, and resistance to age-related degradation may also be considered.
  • ablatability is achieved at a fluence of 230 mJ/cm 2 or less, and more preferably at a fluence of 160 or 150 mJ/cm 2 or less.
  • the ablation threshold is dictated primarily by layer thickness and the loading level and efficiency of the absorber.
  • the topmost layer participates in printing and provides the requisite lithographic affinity difference with respect to substrate 102; in particular, layer 108 is oleophobic and suitable for dry printing.
  • the topmost layer 108 may help to control the imaging process by modifying the heat dissipation characteristics of the printing member at the air-imaging layer interface.
  • layer 108 is a silicone or fluoropolymer.
  • Silicones are based on the repeating diorganosiloxane unit (R2SiO)», where R is an organic radical or hydrogen and n denotes the number of units in the polymer chain.
  • Fluorosilicone polymers are a particular type of silicone polymer wherein at least a portion of the R groups contain one or more fluorine atoms.
  • the physical properties of a particular silicone polymer depend upon the length of its polymer chain, the nature of its R groups, and the terminal groups on the end of its polymer chain. Any suitable silicone polymer known in the art may be incorporated into or used for the surface layer.
  • Silicone polymers are typically prepared by cross-linking (or "curing") diorganosiloxane units to form polymer chains.
  • the resulting silicone polymers can be linear or branched.
  • a number of curing techniques are well known in the art, including condensation curing, addition curing, moisture curing.
  • silicone polymers can include one or more additives, such as adhesion modifiers, theology modifiers, colorants, and radiation-absorbing pigments, for example.
  • Other options include silicone acrylate monomers, i.e., modified silicone molecules that incorporate 'free radical" reactive acrylate groups or "cationic acid” reactive epoxy groups along and/or at the ends of the silicone polymer backbone. These are cured by exposure to UV and electron radiation sources.
  • This type of silicone polymer can also include additives such as adhesion promoters, acrylate diluents, and multifunctional acrylate monomer to promote abrasion resistance, for example.
  • the silicone layer may have a dry coating weight of, for example, 0.5 to 2.5 g/m 2 , with the range 1 to 2.5 g/m 2 being particularly preferred for typical commercial applications.
  • Imaging of the printing member 100 may take place directly on a press, or on a platemaker.
  • the imaging apparatus will include at least one laser device that emits in the region of maximum plate responsiveness, i.e., whose ⁇ closely approximates the wavelength region where the plate absorbs most strongly. Specifications for lasers that emit in the near-IR region are fully described in U.S. Patent Nos. Re. 33,512 ("the '512 patent") and 5,385,092 ("the '092 patent”), the entire disclosures of which are hereby incorporated by reference. Lasers emitting in other regions of the electromagnetic spectrum are well-known to those skilled in the art.
  • laser output can be provided directly to the plate surface via lenses or other beam-guiding components, or transmitted to the surface of a blank printing plate from a remotely sited laser using a fiber-optic cable.
  • a controller and associated positioning hardware maintain the beam output at a precise orientation with respect to the plate surface, scan the output over the surface, and activate the laser at positions adjacent selected points or areas of the plate.
  • the controller responds to incoming image signals corresponding to the original document or picture being copied onto the plate to produce a precise negative or positive image of that original.
  • the image signals are stored as a bitmap data file on a computer.
  • Such files may be generated by a raster image processor ("RIP") or other suitable means.
  • a RIP can accept input data in page-description language, which defines all of the features required to be transferred onto the printing plate, or as a combination of page-description language and one or more image data files.
  • the bitmaps are constructed to define the hue of the color as well as screen frequencies and angles.
  • the imaging apparatus can be configured as a flatbed recorder or as a drum recorder, with the lithographic plate blank mounted to the interior or exterior cylindrical surface of the drum.
  • the requisite relative motion between the laser beam and the plate is achieved by rotating the drum (and the plate mounted thereon) about its axis and moving the beam parallel to the rotation axis, thereby scanning the plate circumferentially so the image "grows" in the axial direction.
  • the beam can move parallel to the drum axis and, after each pass across the plate, increment angularly so that the image on the plate "grows" circumferentially. In both cases, after a complete scan by the beam, an image corresponding (positively or negatively) to the original document or picture will have been applied to the surface of the plate.
  • the beam is drawn across either axis of the plate, and is indexed along the other axis after each pass.
  • the requisite relative motion between the beam and the plate may be produced by movement of the plate rather than (or in addition to) movement of the beam.
  • Examples of useful imaging devices include models of the MAGNUS and TRENDSETTER imagesetters (available from Eastman Kodak Company) that utilize laser diodes emitting near-IR radiation at a wavelength of about 830 nm.
  • Other suitable exposure units include the CRESCENT 42T Platesetter (operating at a wavelength of 1064 nm, available from Gerber Scientific, Chicago, 111.) and the SCREEN PLATERITE 4300 series or 8600 series plate-setter (available from Screen, Chicago, HI.).
  • the printing member is subjected to an aqueous liquid to remove debris where the printing member received imaging radiation, thereby creating an imagewise pattern on the printing member.
  • machine cleaning takes advantage of the preferred imaging-layer coating weights.
  • Preferred processing machines utilize warm water as a cleaning agent applied by spraying onto the plate (as opposed to immersion).
  • Suitable examples include the KONINGS Plate Washer, type KP 650/860 S-CH (Konings GmbH, D-41751, Viersen, Germany) which has two rotary, oscillating brush rollers in the cleaning section), the AS-34 Plate Processor (NES Worldwide Inc., Westfield, MA, which has three rotary, oscillating brush rollers in the cleaner section), and the PRESSTEK
  • WPP85/SC850 Plate Washer (NES Worldwide Inc., which has two rotary brush rollers).
  • CYMEL 300 is a highly methylated, melamine resin supplied at 98% solids by Cytek Industries, Inc., Woodland Park, NJ.
  • MICROPIGMO AMBK-8 is a pigment dispersion that is supplied at 18% solids by Orient Chemical, Osaka, Japan.
  • CYCAT 4040 is a general purpose, p-toluenesulfonic acid catalyst supplied as a 40% solution in isopropanol by Cytek Industries, Inc.
  • WALSRODER E 400 NC is a nitrocellulose damped with 30% IPA purchased from Dow Chemical, Midland, Michigan.
  • BYK 307 is a polyether modified polydimethylsiloxane surfactant supplied by BYK Chemie, Geretsried, Germany.
  • DOWANOL PM is propylene glycol methyl ether available from the Dow Chemical.
  • LUBRIZOL 2062 is supplied by Lubrizol Corporation of Wickliffe, Ohio.
  • nMP N-methyl-2-pyrrolidone, available from Dow Chemical.
  • S0094 is a cyanine near IR dye manufactured by FEW Chemicals GmbH, Bitterfeld-Wolfen, Germany.
  • the image layer 104 was applied to the aluminum substrate using a #7 wire-wound metering rod and then was dried and cured at 282 °F (temperature set on the oven dial) to produce a dried coat weight of 1.1 g/m 2 . Drying and curing were carried out on a belt conveyor oven, SPC Mini EV 48/121, manufactured by Wisconsin Oven Corporation (East Troy, WI).
  • the conveyor was operated at a speed of 3.2 feet/minute (which gives a dwell time of about 40 seconds in the air-heated zone of the oven).
  • the image layer 106 was applied over the image layer 104 using a #6 wire-wound metering rod and men dried and cured at 282 °F to produce a dried coating weight of 1. lg/m 2 .
  • the dwell time in the oven was the same as above.
  • the oleophobic silicone top layer 108 was subsequently disposed on the image layer 106 using the formulation given below.
  • the silicone layer consists essentially of a highly crosslinked network structure produced via the addition or hydrosilylation reaction between the vinyl groups (SiVi) of vmyl-terminated functional silicone and the silyl (SiH) groups of trimeftylsttoxy-teiminated poly(hydrogen methyl siloxane) crosslinker, in the presence of a Pt catalyst complex and an inhibitor.
  • PLY-3 7500P is an end-terminated vinyl-functional silicone resin, with average molecular weight 62,700 g/mol, supplied by Nusil Silicone Technologies,
  • DC Syl Off 7367 is a trimemylsUoxy-terminated poly(hydrogen methylsiloxane) crosslinker manufactured by Dow Corning Silicones (Auburn, MI), which is supplied as a 100% solids solution containing about 30% of 1-ethynylcyclohexane which functions as catalyst inhibitor.
  • CPC 072 is a 1,3 diethyenyl-l,l,3,3-tetramethyldisiloxane Pt complex catalyst manufactured by Umicore Precious Metals (Hoboken-Antwerp, Belgium), which is supplied as a 3% xylene solution.
  • top layer solution was applied to the dried image layer 106 using a #15 wire-wound metering rod and was then dried and cured at 322 °F (temperature set on the oven dial) to produce a dry coating weight of 2.5g/m 2 . Drying and curing were also carried out on a belt conveyor oven at a speed of 3.2 feet/minute, which gives a dwell time of about 40 seconds.
  • Example speed and print quality was assessed by means of a GTO press. Plates were imaged by power series using a custom GATF test target with power range of 88 to 230 mJ/cm 2 , then put through a three-brush KONINGS processor, containing tap water to clean out imaged silicone. The plates were then mounted on press, press was set, impression on, and then sheets were collected.
  • Printed sheets assessed included sheets numbered 25, 50, 100 and sheet 200. The sheets were assessed based upon the energy dose required to achieve a solid 1-pixel area, the imaging speed required to achieve 2% dots, and the imaging speed required to achieve 1% dots (if they exist), within the 88 to 230mJ/cm 2 range. In addition, a generally satisfactory reproduction of the image and its contrast was assessed.
  • Printing plate precursors were imaged on a Kodak Trendsetter image setter, operating at a wavelength of 830 nm, available from Eastman Kodak.
  • a Heidelberg GTO 52 press, single color unit with automatic feed was used in the experiments.
  • the ink used was Toyo King Aqualess Ultra Black MZUS as supplied by Toyo Ink, South Plainfield, NJ.
  • the press blanket used was a Patriot 3000, 4 ply, 0.077 gauge as supplied by Day International (Flint Group Print Media North America, Arden, NC).
  • Label is a measurement of coloration difference (or color or contrast in appearance) between imaged or exposed regions and the unimaged or non- exposed regions of a plate, as determined after imaging (and before development) using a conventional spectrophotometer (such as a MINOLTA CM508i) and the CIELAB system (Commission Internationale de l'Eclairage). No development is needed during this color measuring method.
  • a conventional spectrophotometer such as a MINOLTA CM508i
  • CIELAB system Commission Internationale de l'Eclairage
  • color space is defined in terms of L, a, and b wherein L is a measure of the chroma or brightness of a given color, a is a measure of the red-green contribution of a given color, and b is a measure of the yellow-blue contribution of a given color. Additional information is provided at
  • red spots are caused by undesirable interactions between IR dye and nitrocellulose, which creates an area that does not absorb energy. Red spots do not show up in the wet coating, only once that coating has been applied to a support or another layer and dried in an oven. These areas, if sufficiently large, become unimageable and will show up, undesirably, on the printed paper sheet.
  • the 1-pixel patch was fully solid at 159 mJ/cm 2 , the 2% dots were strong at 88 mJ/cm 2 and the 1% dots were strong at 159 mJ/cm 2 .
  • Unimaged plate color is green, imaged areas are yellow-green at lower exposure doses and orange-green at higher image powers. No red spots were found on the plate. The L value difference is considered acceptable and leads to a plate design having a pleasing appearance and sufficient, usable color contrast.
  • Image layer 106
  • MICROPIGMO AMBK-2 is a pigment dispersion supplied at 20% solids. 50% of the solids is the carbon black material, while the remaining solids is a polyvinyl resin.
  • AMBK-2 is supplied by Orient Chemical, Osaka, Japan.
  • This example uses alternative image layers 104, 106.
  • the substrate and silicone layer are as set forth in Example 1.
  • Image layer 104 [00061]
  • Cymel 303 is a highly methylated, melamine resin that is supplied at 98% solids by Cytek Industries, Inc.
  • Image layer 106 [00063]
  • the 1 -pixel patch of the image was fully solid at 195 mJ/cm 2 , the 2% dots fully formed at 106 mJ/cm 2 .
  • the plate contrast was also similar to Example 1 with an L value difference of 6.11 compared to 5.63 for Example 1. No red spots were found on the plate sample.
  • Example 2 the same substrate, image layer 106, and silicone layer is used as in Example 2, but a different image layer 104 is used.
  • Image layer 104 [00067]
  • Black NC 60K330 is a carbon black pigment and nitrocellulose blend, 31.6% solids as supplied by Pan Technology, Carlstadt, NJ.
  • the 1 -pixel patch was fully solid at 212 mJ/cm 2 , and the 2% dots fully formed at 106 mJ/cm 2 .
  • the plate contrast was stronger than the control, being dark green in the unimaged area and with an orange-green imaged area that gets darker in the highest exposed regions. No red spots were found in the plate sample.
  • Example 7 This example is similar to Example 4, but an untreated aluminum sheet was employed as the support (no graining or anodizing).
  • the printing plate was found to have unacceptable coating adhesion failure. Areas of the image layers were flaking off the aluminum support, especially at the plate edges and where the plate had been clamped into the printing press.
  • the key ingredients are rearranged so that the nitrocellulose is admixed with the IR-absorbing dye and remains in intimate contact with it.
  • the aluminum substrate and silicone layers were as in Example 1.
  • Image layer 104 [00075]
  • Image layer 106
  • Example 2 the same substrate, image layer 106 and silicone layer is used as in Example 2, but a different formulation for image layer 104 is used.
  • Image layer 104 [00080]
  • the 1-pixel patch was fully solid at 159 mJ/cm 2 , and the 2% dots well defined also. No red spots were found on the sample. The plate exhibited good color contrast.
  • Example 2 the same substrate, image layer 104 and silicone layer is used as in Example 1, but a different formulation for image layer 106 is employed.
  • Image layer 106
  • IRT dye is an IR photosensitive bleaching dye as supplied by Showa Denko, Japan.
  • the 1-pixel patch was fully solid at 159 mJ/cm 2 , the 2% dots well presented at 106 mJ/cm 2 , and the 1% dots fully formed at 159 mJ/cm 2 . No red spots were found on inspection of the plate sample. Plate color contrast was deemed average only.
  • Example 1 This example illustrates the use of all key ingredients in one imaging layer.
  • the aluminum substrate and silicone layers were as in Example 1.

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  • Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Thermal Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Printing Plates And Materials Therefor (AREA)

Abstract

La présente invention concerne des éléments d'impression lithographique contenant de la nitrocellulose secs, de type à ablation, (100) qui comprennent des couches d'imagerie adjacentes doubles (104, 106), comprenant toutes deux un absorbeur et au moins une contenant un liant (qui peut comprendre ou être essentiellement constitué d'une résine mélamine). L'absorbeur de la couche contenant de la nitrocellulose est un pigment et cette couche ne contient pas de colorant absorbant, tandis que l'absorbeur de l'autre couche d'imagerie comprend ou est essentiellement constitué d'un colorant.
EP18705194.1A 2017-01-11 2018-01-09 Éléments d'impression lithographique de type à ablation ayant une sensibilité à l'exposition améliorée et procédés associés Pending EP3568301A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US15/403,263 US10124571B2 (en) 2011-05-17 2017-01-11 Ablation-type lithographic printing members having improved exposure sensitivity and related methods
PCT/US2018/012925 WO2018132365A1 (fr) 2017-01-11 2018-01-09 Éléments d'impression lithographique de type à ablation ayant une sensibilité à l'exposition améliorée et procédés associés

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Publication number Priority date Publication date Assignee Title
US3181461A (en) 1963-05-23 1965-05-04 Howard A Fromson Photographic plate
US3902976A (en) 1974-10-01 1975-09-02 S O Litho Corp Corrosion and abrasion resistant aluminum and aluminum alloy plates particularly useful as support members for photolithographic plates and the like
GB1548689A (en) 1975-11-06 1979-07-18 Nippon Light Metal Res Labor Process for electrograining aluminum substrates for lithographic printing
US4577932A (en) 1984-05-08 1986-03-25 Creo Electronics Corporation Multi-spot modulator using a laser diode
US4654213A (en) 1985-09-11 1987-03-31 Cheesebrough-Pond's Inc. Novel anti-microbial systems containing the magnesium sulfate adduct of 2,2'-dithiobis-pyridine-1,1'-dioxide and a water soluble zinc salt
AU674518B2 (en) * 1992-07-20 1997-01-02 Presstek, Inc. Lithographic printing plates for use with laser-discharge imaging apparatus
US5517359A (en) 1995-01-23 1996-05-14 Gelbart; Daniel Apparatus for imaging light from a laser diode onto a multi-channel linear light valve
JPH09131979A (ja) * 1995-11-09 1997-05-20 Toray Ind Inc 直描型水なし平版印刷版原版
JPH09131976A (ja) * 1995-11-08 1997-05-20 Toray Ind Inc 直描型水なし平版印刷版原版
US5802034A (en) 1996-12-09 1998-09-01 Gelbart; Daniel Multi-track optical read/write head
JP2001508001A (ja) * 1997-01-17 2001-06-19 アグフア−ゲヴエルト・ナームローゼ・フエンノートシヤツプ レーザーで像形成可能な記録材料およびそれから製造される無水オフセット印刷用の印刷版
US5861992A (en) 1997-06-20 1999-01-19 Creo Products Inc Microlensing for multiple emitter laser diodes
WO2004011259A1 (fr) * 2002-07-30 2004-02-05 Creo Il. Ltd. Plaque d'impression multicouche a auto-organisation fabriquee en une seule passe

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